From Swedenborg's Works

Arcana Coelestia #59

59. The reason only edible and green plants are mentioned here as food for the natural man is this: While a person is being regenerated and becoming spiritual he is involved constantly in conflict, which is why the Lord's Church is called militant. For before regeneration started, evil desires were in control, since the whole person consisted entirely of evil desires and resulting falsities. During the process of regeneration his desires and falsities cannot be done away with instantly, since that would amount to destroying the whole person; indeed he has not acquired any other life for himself. So for a long time evil spirits are left with him to activate his desires, and so release them in countless ways. Indeed the spirits are left there to do this in order that those desires may be turned by the Lord towards something good, and in this way the person may be reformed. In the hour of conflict evil spirits are present who absolutely hate everything that is good and true, that is, every element of love and faith in the Lord - elements that alone are good and true because they contain eternal life. These evil spirits leave a person with no other food than that which is compared to edible and green plants. But the Lord gives him a food as well that is compared to the plant yielding seed and to the tree in which there is fruit. These are periods of peace and calm attended by their forms of delight and happiness. This cycle occurs repeatedly.

[2] If the Lord did not protect man moment by moment, and in every shortest instant, he would immediately perish, for there is such murderous hatred reigning in the world of spirits against all forms of love and faith in the Lord as to defy description. I can positively declare that this is so, because for several years now, although still in the [physical] body, I have also been in the next life in the company of spirits. I have been surrounded by evil spirits, even the worst of them, sometimes by thousands, who have been allowed to pour out their venom and molest me in every possible way, but who nevertheless could do no harm to the tiniest hair on my head, so well did the Lord protect me. From all these years of experience I have become thoroughly informed about the character of the world of spirits and also about the conflict which people who are being regenerated must inevitably undergo if they are to attain the happiness of eternal life. But because nobody from just a general description can be so well informed as to have a faith free from doubt, these matters in the Lord's Divine mercy will therefore be noted in greater detail later on.